CN103202693B - Magnetic resonance imaging apparatus - Google Patents
Magnetic resonance imaging apparatus Download PDFInfo
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- CN103202693B CN103202693B CN201310003580.5A CN201310003580A CN103202693B CN 103202693 B CN103202693 B CN 103202693B CN 201310003580 A CN201310003580 A CN 201310003580A CN 103202693 B CN103202693 B CN 103202693B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
- G01R33/48—NMR imaging systems
- G01R33/4818—MR characterised by data acquisition along a specific k-space trajectory or by the temporal order of k-space coverage, e.g. centric or segmented coverage of k-space
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
- G01R33/48—NMR imaging systems
- G01R33/54—Signal processing systems, e.g. using pulse sequences ; Generation or control of pulse sequences; Operator console
- G01R33/56—Image enhancement or correction, e.g. subtraction or averaging techniques, e.g. improvement of signal-to-noise ratio and resolution
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
- G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
- G01R33/48—NMR imaging systems
- G01R33/54—Signal processing systems, e.g. using pulse sequences ; Generation or control of pulse sequences; Operator console
- G01R33/56—Image enhancement or correction, e.g. subtraction or averaging techniques, e.g. improvement of signal-to-noise ratio and resolution
- G01R33/5607—Image enhancement or correction, e.g. subtraction or averaging techniques, e.g. improvement of signal-to-noise ratio and resolution by reducing the NMR signal of a particular spin species, e.g. of a chemical species for fat suppression, or of a moving spin species for black-blood imaging
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Abstract
The feature of the magnetic resonance imaging apparatus of embodiment is, possess: configuration part, setting pulse train, this pulse train has fat suppression pre-pulse and the data collection train of pulse for collecting image reconstruction echo data, and, between the front end of described fat suppression pre-pulse to described data collection train of pulse, be provided with multiple ghost pulses; Data collection unit, applies based on the high-frequency impulse of the described pulse train set by described configuration part and gradient magnetic field pulses subject, and collects described echo data; And image production part, the image of described subject is reconstructed according to collected described echo data; The application time of described multiple ghost pulses or the flip angle of described multiple ghost pulses can adjust.
Description
Technical field
The present invention relates to magnetic resonance imaging apparatus.
Background technology
Magnetic resonance imaging apparatus is following camera head: the high frequency (RF:RadioFrequency utilizing Larmor frequency, radio frequency) nuclear spin of signal to the subject be positioned in magnetostatic field encourages, and the magnetic resonance signal according to producing from subject along with excitation carrys out reconstructed image.
In the field of magnetic-resonance imaging, there will be a known and the signal (fat signal) from the fat in subject is carried out as not signal the various fat suppression methods that suppress.The fat suppression method in the past generally used has CHESS(chemicalshiftselective: chemical shift is selected) method, SPIR(spectralpresaturationwithinversionrecovery: the presaturation of inversion recovery He Ne laser) method (also referred to as SPECIR), STIR(shortTIinversionrecovery: inversion recovery in short-term) method etc.
Wherein, CHESS method make use of water phantom to have the different this point of 3.5ppm from the resonant frequency of fat-body mould, and only frequency selectivity ground suppresses the method for fat signal.Therefore, CHESS method is also referred to as the fat suppression method of frequency selectivity.In CHESS method, before carrying out data collection, the high-frequency impulse (also referred to as CHESS pulse) of the resonant frequency with fat is put on subject with the flip angle of 90 ° (flipangle) usually.By the applying of CHESS pulse, topple over 90 ° with only having the longitudinal magnetization frequency selectivity of fat.Then, if apply be called as spoilerpulse(damage pulse) gradient magnetic field pulses, then fat cross magnetization can disperse, disappear.Further, if start data collection after applying spoilerpulse, then data collection can be carried out under the state that inhibit fat signal.
SPIR method is also one of frequency selectivity fat suppression method of the difference of the resonant frequency utilizing water phantom and fat-body mould.In SPIR method also, subject is applied to the high-frequency impulse (also referred to as SPIR pulse) of the resonant frequency with fat before data collection.But the flip angle of SPIR pulse is set between 90 ° to 180 ° usually.If be applied with SPIR pulse, then the longitudinal magnetization of fat only topples over the angle corresponding with flip angle frequency selectivity.The flip angle of SPIR pulse is between 90 ° to 180 °, and therefore, negative value is got in the longitudinal magnetization being just applied with the postimpulse fat of SPIR.Then, make the longitudinal magnetization of fat increase along with the time owing to longitudinally relaxing, from negative value to revert to gradually through zero crossing (nullpoint) on the occasion of.The resume speed longitudinally relaxed relaxes (T1 mitigation) by the longitudinal direction of fat to decide.Will from applying SPIR pulse to image reconstruction data collection starts time of (more strictly speaking, when applying to the initial driving pulse of data collection), be called the reversing time (TI:inversiontime) in SPIR method.In SPIR method, by making above-mentioned reversing time consistent with from the time applied SPIR pulse to the longitudinal magnetization zero crossing of fat, thereby, it is possible to carry out under the state that inhibit fat signal only from the data collection of water signal.
Above-mentioned 2 camera methods are all frequency selectivity fat suppression methods, but on the other hand, STIR method is non-frequency-selective fat suppression method.STIR method is the difference of the longitudinal relaxation time (T1 relaxation time) utilizing fat signal and water signal energetically, namely utilizes this point shorter in longitudinal relaxation time of water signal of longitudinal relaxation time of fat signal, suppresses the camera method of fat.Before data collection, apply to subject the high-frequency impulse (STIR pulse) that flip angle is the non-frequency-selective of 180 °, the longitudinal magnetization of fat-body mould and water phantom topples over 180 ° simultaneously, makes both sides become negative value.The longitudinal magnetization of fat signal and water signal recovers to certain positive direction gradually after applying STIR pulse, but due to longitudinal relaxation time of fat signal shorter than longitudinal relaxation time of water signal, therefore, the longitudinal magnetization of fat signal first can arrive zero point.Same with SPIR method, will from applying STIR pulse to image reconstruction data collection starts (more strictly speaking, when applying to the initial driving pulse of data collection) time, be called the reversing time (TI:inversiontime) in STIR method.In STIR method, by making above-mentioned reversing time consistent with from the time applied STIR pulse to the longitudinal magnetization zero crossing of fat, can carry out under the state that inhibit fat signal only from the data collection of water signal.
STIR method, owing to being non-frequency-selective fat suppression method, therefore has not by the advantage of the impact of the inhomogeneities of magnetostatic field.But there is following shortcoming: when data collection, the longitudinal magnetization (negative value) of water signal is little compared with not applying the situation of STIR pulse, and therefore, SN ratio (signal to noise ratio) diminishes, or, to guarantee that the SN specified is than then camera time can be elongated.
On the other hand, CHESS method and SPIR method are owing to being frequency selectivity fat suppression method, and therefore, the longitudinal magnetization of water signal can not be affected because of the applying of CHESS pulse or SPIR pulse, the reduction of the SN ratio that STIR method can not be caused such.But these camera methods, owing to being frequency selectivity fat suppression method, are therefore easily subject to the impact of Distribution of Magnetic Field, if the inhomogeneities of magnetostatic field B0 or RF magnetic field B1 Existential Space, then the spatial distribution of the fat after suppressing is also easily uneven.
Therefore, the camera method that spatially can suppress fat in the frequency selectivity fat suppression method that the reduction of SN ratio is less is equably proposed.Such as, describe in patent documentation 1 after applying SPIR pulse and then apply CHESS pulse, then start the camera method of data collection.According to this camera method, the most fat signal that do not disappear in SPIR method reduces further due to the applying of CHESS pulse, therefore, it is possible to spatially equably and suppress fat signal with higher degree of suppression.
Look-ahead technique document
Patent documentation
Patent documentation 1: JP 2008-264499 publication
In fat suppression method described in citing document 1, can spatially equably and with higher degree of suppression suppress fat, therefore, be very effective camera method from the viewpoint of fat suppression.And on the other hand, in diagnostic imaging, because fat is by extra-inhibitory, sometimes can cause bad on the contrary.Such as, injecting contrast agent diagnoses the diagnostic imaging of the tumor of breast etc. to be exactly one example.A large amount of mammary gland is had around tumor.If tumor exists, then the signal intensity from tumor during contrast agent arrival tumor portion is usually high than the signal intensity of the mammary gland from surrounding.If the degree appropriateness of fat suppression, the fat signal so spatially in a big way remained can cover a large amount of mammary gland signals, and thus mammary gland signal becomes not obvious, result, easily identifies the signal from tumor.
On the other hand, if fat is spatially too evenly suppressed, then mammary gland signal can become clearly.Particularly, the quantity of mammary gland is a lot, therefore, even if high from the signal intensity of mammary gland from the signal intensity ratio of tumor, also can make to be difficult to identify tumor signal due to the mammary gland signal be positioned at around tumor.
Therefore, urgent expectation is a kind of is not the magnetic resonance imaging apparatus put forward high-fat degree of suppression simply but degree of suppression can be adjusted to desired value.
Summary of the invention
The feature of the magnetic resonance imaging apparatus of embodiment is, possess: configuration part, setting pulse train, this pulse train has fat suppression pre-pulse and the data collection train of pulse for collecting image reconstruction echo data, and, between the front end of described fat suppression pre-pulse to described data collection train of pulse, be provided with multiple ghost pulses; Data collection unit, applies based on the high-frequency impulse of the described pulse train set by described configuration part and gradient magnetic field pulses subject, and collects described echo data; And image production part, the image of described subject is reconstructed according to collected described echo data; The application time of described multiple ghost pulses or the flip angle of described multiple ghost pulses can adjust.
Accompanying drawing explanation
Fig. 1 is the figure of the overall structure example representing magnetic resonance imaging apparatus.
Fig. 2 is the figure of the example representing the pulse train in the past with good fat suppression characteristic.
Fig. 3 illustrates the figure wishing the background of the adjustment of fat suppression degree.
Fig. 4 is the figure of an example of the pulse train representing the first embodiment.
Fig. 5 is the figure of an example of the pulse train representing the second embodiment.
Fig. 6 is the figure of the example represented the result that the relation between forceless pulse strokes per minute and the recovery of fat signal measures.
Fig. 7 is the figure of the detailed example of the pulse train representing the second embodiment.
Fig. 8 is the figure of the order example of the phase code represented in data collection train of pulse.
Fig. 9 is the figure of other examples of the fat suppression pre-pulse represented in the second embodiment.
Figure 10 is the figure of an example of the pulse train representing the 3rd embodiment.
Figure 11 is the figure of an example of the pulse train representing the 4th embodiment.
Figure 12 is the first figure of the order example of the phase code represented in the data collection train of pulse in the 4th embodiment.
Figure 13 is the second figure of the order example of the phase code represented in the data collection train of pulse in the 4th embodiment.
Figure 14 is the 3rd figure of the order example of the phase code represented in the data collection train of pulse in the 4th embodiment.
Detailed description of the invention
Below, based on accompanying drawing, embodiments of the present invention are described.
(1) magnetic resonance imaging apparatus
Fig. 1 is the integrally-built block diagram of the magnetic resonance imaging apparatus 1 represented in present embodiment.As shown in Figure 1, magnetic resonance imaging apparatus 1 possesses: the magnetostatic field Magnet 22 forming the tubular of magnetostatic field; The unifluxor circle 24 of the tubular arranged in coaxial mode in the inner side of magnetostatic field Magnet 22; Gradient magnetic field coil 26; Send with or receive with RF coil 28; Control system 30; Be placed with diagnostic bed 32 of subject (patient) P; Etc..And control system 30 possesses: magnetostatic field power supply 40, unifluxor circle power supply 42, gradient magnetic power supply 44, RF transmitter 46, RF receptor 48, diagnostic bed driving device 50, sequence controller 56 and computer 58 etc.In addition, computer 58 as its internal structure, and has arithmetic unit 60, input equipment 62, display device 64 and storage device 66 etc.
Magnetostatic field Magnet 22 is connected with magnetostatic field power supply 40, forms magnetostatic field by the electric current supplied from magnetostatic field power supply 40 in shooting space.Unifluxor circle 24 is connected with unifluxor circle power supply 42, by the electric current that supplies from unifluxor circle power supply 42 by magnetostatic field homogenization.Magnetostatic field Magnet 22 is in most cases made up of superconducting coil, is connected and is supplied to electric current when excitation with magnetostatic field power supply 40, but once after being excited, generally becomes notconnect state.In addition, also can be, magnetostatic field power supply 40 is not set, and form magnetostatic field Magnet 22 with permanent magnet.
Gradient magnetic power supply 44 is made up of X-axis gradient magnetic power supply 44x, Y-axis gradient magnetic power supply 44y and Z axis gradient magnetic power supply 44z.In addition, in FIG, using magnetostatic field with Magnet 22 and unifluxor circle 24 axially as Z-axis direction, using vertical as Y-axis, using the direction orthogonal with these directions as X axis.
Gradient magnetic field coil 26 has X-axis gradient magnetic field coil 26x, Y-axis gradient magnetic field coil 26y and Z axis gradient magnetic field coil 26z, is formed as tubular in the inner side of magnetostatic field Magnet 22.X-axis gradient magnetic field coil 26x, Y-axis gradient magnetic field coil 26y and Z axis gradient magnetic field coil 26z are connected with X-axis gradient magnetic power supply 44x, Y-axis gradient magnetic power supply 44y and Z axis gradient magnetic power supply 44z respectively.
By the electric current supplied respectively to gradient magnetic field coil 26x, 26y, 26z from each gradient magnetic power supply 44x, 44y, 44z, in shooting space, form gradient magnetic Gx, Gy, Gz of X-axis, Y-axis and Z-axis direction respectively.
Gradient magnetic Gx, Gy, Gz of 3 axis of device coordinate system are synthesized, at random can set all directions of slice direction gradient magnetic Gss, phase-encoding direction gradient magnetic Gpe as logic axle and readout direction (frequency coding direction) gradient magnetic Gro.Each gradient magnetic of slice direction, phase-encoding direction and readout direction is overlapped in magnetostatic field.
RF transmitter 46, based on the control information inputted from sequence controller 56, generates the RF pulse of the Larmor frequency for causing nuclear magnetic resonance, NMR, and this RF pulse is sent to transmission RF coil 28.Have in RF coil 28: send RF pulse and receive from the magnetic resonance signal (MR signal) of subject receiving and transmitting signal whole-body coil (WBC:wholebodycoil), be arranged at the reception coils special (also referred to as local coil) etc. of vicinity of diagnostic bed 32 or subject P.
MR signal received by RF coil 28 is supplied to RF receptor 48 via signal cable.
RF receptor 48 is to the MR signal received, after implementing the various signal processing such as enlarge leadingly, intermediate frequency conversion, phase detection, low frequency amplification, filtering, implement A/D(analogtodigital: mould/number) conversion, thus, the digitized initial data as complex data (rawdata) is generated.The initial data of the MR signal of generation is inputed to sequence controller 56 by RF receptor 48.
Arithmetic unit 60 possesses processor etc. and forms, and except carrying out the Systematical control of magnetic resonance imaging apparatus 1 entirety, also carries out image reconstruction process, various image procossing.
Sequence controller 56 makes according to being stored in the imaging conditions of the regulation in the storage device 66 of computer 58 or the instruction of pulse train and the arithmetic unit 60 based on these, produces gradient magnetic Gx, Gy, Gz and RF pulse.In addition, the MR signal that these R gradient magnetic Gx, Gy, Gz and RF pulses of response receive by sequence controller 56, inputs from RF receptor 48 as initial data, and exports arithmetic unit 60 to.
Arithmetic unit 60, to inputted initial data, carries out including the reconstruction processing of inverse Fourier transform etc. or various image procossing, generates the view data of subject.The view data generated is shown in display device 64.Input equipment 62 is used when being inputted imaging conditions or various information by user operation.
In the present embodiment, the configuration part that above-mentioned arithmetic unit 60 comprises the imaging conditions of various pulse train as setting plays function.There is fat suppression pre-pulse described later and set by this configuration part for the pulse train of the data collection train of pulse collecting image reconstruction echo data.In addition, also set by configuration part from fat suppression pre-pulse to the adjustable time delay, forceless pulse strokes per minute described later etc. arranged between the front end of data collection train of pulse.
Based on the imaging conditions of the pulse train set by configuration part etc., sequence controller 56 drives RF transmitter 46, gradient magnetic power supply 44, applies RF pulse based on set pulse train or gradient magnetic field pulses via RF coil 28 or gradient magnetic field coil 26x, 26y, 26z to subject.The magnetic resonance signal (MR signal) produced from subject accordingly with the applying of these pulses is received by RF receptor 48, is sent to sequence controller 56 as echo data (initial data).Like this, above-mentioned sequence controller 56, RF transmitter 46, gradient magnetic power supply 44, RF coil 28, gradient magnetic field coil 26x, 26y, 26z, RF receptor 48 etc. form the data collection unit of present embodiment.
For the echo data (initial data) being sent to sequence controller 56, arithmetic unit 60 carries out comprising the reconstruction processing of inverse Fourier transform etc. or various image procossing, generates the view data of subject.In other words, arithmetic unit 60 plays function as the image production part of present embodiment.
(2) pulse train (the first embodiment)
As mentioned above, as the camera method of the fat signal not wanting signal, various pulse train is proposed as suppressing.Fig. 2 (a) is the figure of an example of the fat suppression pulse train shown as past case disclosed in patent documentation 1.In addition, Fig. 2 (b) is the figure of the change shape of the longitudinal magnetization of the fat signal schematically represented under this pulse train.In the pulse train shown in Fig. 2 (a), namely the RF pulse of frequency selectivity had the SPIR pulse (the first fat suppression pulse) of the resonant frequency of fat, there is the CHESS pulse (the second fat suppression pulse) of the resonant frequency of fat equally, as the prepulsing before data collection, be applied to subject.The flip angle of SPIR pulse is set between 90 ° to 180 ° usually.In addition, the flip angle of CHESS pulse is set as 90 °.
If be applied with SPIR pulse, then as shown in Fig. 2 (b), the angle corresponding with flip angle is toppled on the longitudinal magnetization frequency selectivity ground of fat.The flip angle of SPIR pulse is between 90 ° to 180 °, and therefore, negative value is got in the longitudinal magnetization of the fat after just applying.Then, make the longitudinal magnetization of fat increase together along with the time owing to longitudinally relaxing, from negative value through zero crossing gradually on the occasion of recovery.The resume speed longitudinally relaxed relaxes (T1 mitigation) by the longitudinal direction of fat and decides.By the time from applying SPIR pulse to longitudinal magnetization returns to zero point, be called the reversing time (TI:inversiontime) in this camera method.In the pulse train shown in Fig. 2 (a), from applying SPIR pulse after reversing time (TI), apply CHESS pulse.
Magnetostatic field (B0) and high frequency magnetic field (B1) spatially completely evenly and longitudinal relaxation time of fat get identical value ideally, from applying SPIR pulse after reversing time, the longitudinal magnetization of fat is put also through zero crossing in Space Equal-position.But magnetostatic field (B0), high frequency magnetic field (B1) are spatially not exclusively evenly.As a result, be just applied with the postimpulse longitudinal magnetization of SPIR-M0 ' as shown in Fig. 2 (b), spatially not exclusively evenly, after reversing time TI, be not also entirely zero.
Thus, in the pulse train shown in Fig. 2 (a), rise after reversing time TI in applying SPIR pulse, apply the CHESS pulse as the second fat suppression pulse.By applying CHESS pulse, topple over 90 ° in reversing time TI make the not disappear longitudinal magnetization of most fat.Then, as shown in Figure 2 (a) shows, apply damage pulse (spoilerpulse) and make the cross magnetization composition of fat disperse, disappear.Then, such as, use and be dependent on FFE(FastFieldEcho) train of pulse of method, namely use multiple driving pulses that flip angle is less, change phase code amount and collect echo data.
In the pulse train shown in Fig. 2 (a), by using the fat suppression pulse of SPIR pulse and these 2 frequency selectivities of CHESS pulse, can spatially equably and suppress fat signal fully.
But as mentioned above, in diagnostic imaging, the undue fat that suppresses sometimes on the contrary can be bad.Fig. 3 is the figure that one example is described.Fig. 3 observes with 1 dimension (such as X-direction) to inject contrast agent to diagnose the concept map during diagnostic image of the tumor of breast etc.A large amount of mammary gland is had around tumor.If have tumor, then when contrast agent reaches tumor portion, the signal intensity from tumor is usually high than the signal intensity of the mammary gland from surrounding.If the degree appropriateness of fat suppression, the fat signal so spatially in a big way remained can cover a large amount of mammary gland signals, and therefore mammary gland signal becomes not obvious, result, easily identifies the signal from this tumor.On the other hand, if fat is spatially too evenly suppressed, then mammary gland signal can become obvious.Particularly, the quantity of mammary gland is a lot, therefore, even if high from the signal intensity of mammary gland from the signal intensity ratio of tumor, also can make to be difficult to identify tumor signal due to the mammary gland signal be positioned at around tumor.This trend is at MIP(maximumintensityprojection: maximum intensity projection) remarkable especially in image.
In the pulse train of the present embodiment of following explanation, it not the degree of suppression determining fat entirely, but in pulse train, set adjustable parameter, by adjusting this parameter, make it possible to adjustment fat suppression degree, as its result, easily tumor signal can be detected from a large amount of mammary gland signals.Below, the pulse train of present embodiment is specifically described.
The figure of Fig. 4 (a) to be the figure of the pulse train that the first embodiment is described, Fig. 4 (b) be variation of the longitudinal magnetization schematically representing fat signal.The pulse train of the first embodiment is as fat suppression prepulsing, SPIR pulse and these 2 frequency selectivity fat suppression pulse of CHEAA pulse are used in the same manner with Fig. 2 (a), but about arranging TA this point adjustable time delay between data collection train of pulse and fat suppression prepulsing, differ widely with the pulse train in the past shown in Fig. 2 (a).
As mentioned above, under SPIR pulse, the longitudinal magnetization toppled over for the fat of negative value almost reverts to zero point after reversing time TI, and by the applying of the CHESS pulse in this moment, longitudinal magnetization is adequately suppressed.If just make data collection train of pulse start after being just applied with CHESS pulse, then can carry out the data collection under the high state of fat suppression degree, but fat signal is by extra-inhibitory, sometimes bad on the contrary in diagnostic imaging.
On the other hand, recover lentamente after being suppressed to the fat signal of zero by applying CEHSS pulse.The Size-dependent of the recovery extent of fat signal, i.e. fat signal is in the elapsed time from applying CEHSS pulse.
Therefore, in the pulse train of the first embodiment, to rise with prepulsing (more particularly, apply CHESS pulse) between the front end to data collection train of pulse in applying fat suppression, T time delay not applying any pulse is set
a, by suitably adjusting T time delay
a, adjust the size of the recovery of the fat signal of suppressed mistake, result, adjustment fat suppression degree.
(3) second embodiments
To be the figure of the pulse train that the second embodiment is described, Fig. 5 (b) be Fig. 5 (a) schematically represents the figure of the variation of the longitudinal magnetization of the fat signal under this pulse train.The difference of the second embodiment and the first embodiment is, the pulse train of the first embodiment arranges the adjustable time delay not applying any pulse between the front end of fat suppression prepulsing to data collection train of pulse, on the other hand, the pulse train of the second embodiment arranges multiple ghost pulses (dummypulse) between the front end of fat suppression prepulsing to data collection train of pulse.
Ghost pulses is the RF pulse not being attended by data collection, and the interval of ghost pulses is set as the interval identical with the interval of each driving pulse in data collection train of pulse.In addition, the mid frequency of ghost pulses is not and the resonant frequency as the not fat of signal, but consistent with the resonant frequency of the water as desired signal.
The pulse train of the first embodiment arranges adjustable time delay, fat signal degree of suppression can be adjusted to desired value thus, but data collection train of pulse in time delay through just starting at once later, therefore, transitional variation can be produced to desired signal (being water signal in this situation), artifact may be produced because of this transitional Fluctuation of analytical signal.
On the other hand, in the pulse train of the second embodiment, be provided with as ghost pulses with the driving pulse same intervals of data collection train of pulse and multiple RF pulses of same centre frequency, therefore, in the start time of data collection train of pulse, the foment of water signal reaches steady statue, thus can just collect stable water signal from data collection train of pulse at the beginning.As a result, the artifact caused by above-mentioned transitional Fluctuation of analytical signal can be suppressed.
On the other hand, the mid frequency of ghost pulses is different from the resonant frequency of fat signal, and therefore, the variation of fat signal can not be subject to much impacts because of the applying of ghost pulses.Therefore, the quantity of adjustment ghost pulses, is equivalent in fact adjustment and applies the recovery extent that CHESS adjusts fat signal postimpulse time delay.
Fig. 6 is the figure of the example represented the result that the quantity of ghost pulses and the recovery extent of fat signal measure.The transverse axis of figure is forceless pulse strokes per minute, and the longitudinal axis is the size of the fat signal after standardization.Mensuration is carried out the body mould that fat is simulated with the position configuration of 2, left and right in regulation region.As shown in Figure 6, by the strokes per minute of adjustment forceless pulse, the size of fat signal can be adjusted in a big way.
Fig. 7 is the figure of the example more specifically of the pulse train representing the second embodiment.In the figure 7, upper strata is RF pulse, and the second layer is section selection gradient magnetic field pulses, and third layer is phase code gradient magnetic field pulses, and the 4th layer is extraction gradient magnetic field pulses, and layer 5 is echo data.
In addition, data collection train of pulse illustrated in Fig. 7 and the data collection train of pulse of following explanation are used for use and are dependent on FFE(FastFieldEcho: high speed field echo) train of pulse of method, use multiple driving pulses that flip angle is less, change phase code amount to collect echo data at a high speed.But, the data collection train of pulse can applied in the present embodiment is not limited to FFE method, such as, also can be SE(SpinEcho: spin echo) method, high speed SE(FSE: high speed spin echo) method, in FSE method, combine half Fourier techniques and the FASE(FastAsymmetricSE obtained) method or EPI(EchoPlanarImaging: echo-planar imaging) method.
On the other hand, in which kind of data collection train of pulse all, the phase code amount of the front end of data collection train of pulse be preferably zero or close to zero value.The significant data of the contrast of phase code amount to be the echo data near zero be domination integral image, by being that echo data near zero is arranged near the front end of data collection train of pulse by phase code amount, the image of the fat suppression degree after reflecting adjustment more delicately can be obtained.
When the phase code amount of the front end by data collection train of pulse is set as zero, also various mode can be expected.Fig. 8 shows the figure of its several example.
Fig. 8 (a) is the figure of the order of the phase code amount represented under so-called center order (centricorder).In data collection train of pulse after ghost pulses, initial collection phase code amount is zero (k
0) echo data, then, make symbol positive and negative alternately change as k
1, k
-1, k2, k
-2increase phase code amount successively like that.Fig. 8 (b) shows the order of following phase code amount: after ghost pulses, makes phase code amount from phase code amount zero (k
0) increase to positive direction, after reaching positive maximum, change polarity and the direction of phase code amount from negative maximum towards zero is reduced.In addition, Fig. 8 (c) shows the order of following phase code amount: after ghost pulses, contrary with Fig. 8 (b), makes phase code amount from phase code amount zero (k
0) increase to negative direction, after reaching negative maximum, change polarity and the direction of phase code amount from positive maximum towards zero is reduced.
T adjustable time delay in first embodiment
a, adjustable ghost pulses in the second embodiment quantity, concrete numerical value can be inputted via input equipment 62 by user.In addition, in this second embodiment, also can be, user's input delay time T
a, by inputted T time delay
aforceless pulse strokes per minute is obtained at interval (TR) divided by the driving pulse of the data collection train of pulse of setting in addition.Division arithmetic itself is undertaken by device.In this case, even if change the interval of driving pulse, time delay T
aalso keep certain, therefore, obtain the fat signal intensity of identical degree of suppression all the time.
In addition, also can be or not direct input delay time T
aand the numerical value of the quantity of ghost pulses, but the degree of fat suppression degree is divided into such as " greatly ", " in ", " little " this 3 stage degree, using this differentiation as the deferred message relevant with time delay, inputted by user.In this case, with " greatly ", " in ", the differentiation of " little " accordingly pre-assigned time delay T
aand the numerical value of the quantity of ghost pulses is set by device, decrease the operation burden of user.
Above as fat suppression pre-pulse, describe the example of the combination of 2 the frequency selectivity fat suppression pulse be made up of SPIR pulse and CHESS pulse, but the fat suppression pre-pulse in present embodiment is not limited thereto.
Such as, as shown in Fig. 9 (a), also can be, using SPIR pulse and be almost located at same position the combination of continuous print 2 CHESS pulses as fat suppression pre-pulse.Or, as shown in Figure 9 (b), also can be, using 1 CHESS pulse as fat suppression pre-pulse.In addition, shown in Fig. 9 (c), also can be, using 1 SPIR pulse as fat suppression pre-pulse.When Fig. 9 (c), refer to adjustable time delay become zero from the longitudinal magnetization of the fat of toppling over due to SPIR pulse moment time to the front end of data collection train of pulse.In addition, the moment that the longitudinal magnetization that ghost pulses is inserted in fat becomes zero to data collection train of pulse front end between.
(4) the 3rd embodiments
To be the figure of the pulse train that the 3rd embodiment is described, Figure 10 (b) be Figure 10 (a) schematically represents the figure of the variation of the longitudinal magnetization of the fat signal under this pulse train.The difference of the 3rd embodiment and the second embodiment is, the flip angle of the ghost pulses in the pulse train of the second embodiment is identical with the flip angle of the driving pulse of data collection train of pulse, on the other hand, in the third embodiment, the flip angle of ghost pulses is set be greater than the flip angle of the driving pulse of data collection train of pulse.
Such as, be 10 ° ~ 20 ° relative to the flip angle of each driving pulse in data collection train of pulse (FFE method), the flip angle of ghost pulses be set as significantly such as 60 °.
By setting the flip angle of ghost pulses significantly, as shown in Figure 10 (b), the recovery quantitative change of known fat is large.Therefore, in the third embodiment, utilize this characteristic, the flip angle of the flip angle of ghost pulses compared to the driving pulse of data collection train of pulse is set significantly.As a result, the recovery time of fat can be done sth. in advance, the fat suppression degree desired by can being realized by the ghost pulses of lesser amt.Therefore, pulse train entirety shortens, and can shorten data collection time.
As the 3rd his variation of embodiment, also can be do not make ghost pulses flip angle separately certain, but make it change.Such as, in order to make the change of the flip angle of ghost pulses mild, and be set to and make ghost pulses flip angle separately gently become large.Such as, when the flip angle of driving pulse is set to 20 °, the flip angle of ghost pulses is changed linearly from 20 ° to 60 °.
(5) the 4th embodiments
Figure 11 (a) is the figure of the pulse train that the 4th embodiment is described, Figure 11 (b) is the figure of the variation of the longitudinal magnetization schematically representing fat signal.Variation and first ~ the 3rd embodiment of longitudinal magnetization itself does not have relatively big difference.In the pulse train of embodiment before, between fat suppression prepulsing and data collection train of pulse, set the time delay (the first embodiment) of not carrying out data collection, the ghost pulses (second, third embodiment) not carrying out data collection is set between fat suppression prepulsing and data collection train of pulse.
On the other hand, in the 4th embodiment, pulse train is, and then setting data collection train of pulse after fat suppression prepulsing, on the other hand, in data collection train of pulse with phase code amount zero (k
0) between corresponding driving pulse and the front end of data collection train of pulse, multiple driving pulses of the adjustable quantity corresponding with beyond phase code amount zero are set.
Figure 12 (a) shows an example of the order of the phase code in the second embodiment, is the figure identical with Fig. 8 (b).In this second embodiment, after ghost pulses, have from phase code amount zero (k
0) the data collection train of pulse that starts.
On the other hand, Figure 12 (b), (c) are the figure of an example of the order of the phase code represented in the pulse train of the 4th embodiment, all ghost pulses is not set, and then starts after fat suppression prepulsing to be collected in the echo data used in image reconstruction.But, with phase code amount zero (k
0) shown in corresponding driving pulse embodiment as in the previous like that, be not the front end being positioned at data collection train of pulse, but be positioned at the middle part of data collection train of pulse.Further, from the front end of data collection train of pulse to phase code amount zero (k
0) between, be configured with for collecting multiple driving pulses that phase code amount is the echo data beyond zero in the mode of its quantity of adjustable.By adjustment from the front end of data collection train of pulse to phase code amount zero (k
0) between the quantity of driving pulse, phase code amount zero (k can be adjusted
0) size of fat signal in moment.In other words, in the 4th embodiment, be positioned at from the front end of data collection train of pulse to phase code amount zero (k
0) between driving pulse have concurrently as the function of data collection driving pulse and the function as the ghost pulses in second, third embodiment.As a result, can the length of chopped pulse sequence, can data collection time be shortened.
As shown in Figure 12 (b), (c), when data collection train of pulse be its front end correspond to the train of pulse that negative phase code amount and phase code amount increase with regulation amplitude from negative phase code to positive direction, by the negative phase code amount of front end can be adjusted, thus can adjust and make phase code amount zero (k
0) before driving pulse as ghost pulses play function time forceless pulse strokes per minute.
On the other hand, as shown in Figure 13 (a) and (b), when data collection train of pulse be its front end correspond to the train of pulse that positive phase code amount and phase code amount reduce with regulation amplitude from positive phase code to negative direction, by the positive phase code amount of front end can be adjusted, thus can adjust and make phase code amount zero (k
0) before driving pulse as ghost pulses play function time forceless pulse strokes per minute.
In addition, as shown in Figure 14 (a) and (b), also can be, in the front end of data collection train of pulse to phase code amount zero (k
0) between, configure successively from the absolute value of phase code amount is larger, make driving pulse corresponding to the phase code amount larger with these double as ghost pulses.
As discussed above, according to the magnetic resonance imaging apparatus of pulse train with above-mentioned each embodiment, not the degree of suppression increasing fat simply, but degree of suppression can be adjusted to desired value.
Describe several embodiment of the present invention, these embodiments are pointed out as an example, are not intended to limit scope of invention.These embodiments can be implemented in other various modes, can carry out various omission, displacement and change in the scope not departing from invention aim.These embodiments and distortion thereof are included in scope of invention and aim, are included in equally in invention described in claims and equivalent scope thereof.
Claims (13)
1. a magnetic resonance imaging apparatus, is characterized in that, possesses:
Configuration part, setting pulse train, this pulse train has fat suppression pre-pulse and the data collection train of pulse for collecting image reconstruction echo data, and, the moment that the longitudinal magnetization of having got the fat of negative value in the applying by described fat suppression pre-pulse is restored to zero to described data collection train of pulse front end between there is adjustable time delay;
Data collection unit, applies based on the high-frequency impulse of the described pulse train set by described configuration part and gradient magnetic field pulses subject, and collects described echo data; And
Image production part, reconstructs the image of described subject according to collected described echo data.
2. magnetic resonance imaging apparatus as claimed in claim 1, is characterized in that,
Described data collection train of pulse has multiple driving pulse,
Multiple ghost pulses is provided with during described adjustable time delay,
Described multiple driving pulse interval is separately identical with described multiple ghost pulses interval separately,
The application time of described multiple ghost pulses is adjusted by changing the quantity of described ghost pulses, and by the adjustment of the application time of described multiple ghost pulses, described time delay is adjusted.
3. magnetic resonance imaging apparatus as claimed in claim 2, is characterized in that,
Also possess:
Input part, inputs the application time information relevant with described application time in the mode changed;
Described application time is set based on inputted described application time information,
The quantity of described ghost pulses was obtained divided by the interval of described driving pulse by the time from described fat suppression pre-pulse to the front end of described data collection train of pulse.
4. magnetic resonance imaging apparatus as claimed in claim 2, is characterized in that,
Described fat suppression pre-pulse be frequency selectivity make the longitudinal magnetization of fat to be greater than 90 degree and the flip angle the being less than 180 degree SPIR pulse carrying out toppling over,
Between described SPIR pulse and the front end of described data collection train of pulse, the longitudinal magnetization of fat is made to carry out the CHESS pulse toppled over the flip angle of 90 degree with being also provided with frequency selectivity,
The interval of described SPIR pulse and described CHESS pulse is the time from applying described SPIR pulse to the longitudinal flux cancellation of the fat of toppling over due to described SPIR pulse,
The application time of described multiple ghost pulses is the time from described CHESS pulse to the front end of described data collection train of pulse.
5. magnetic resonance imaging apparatus as claimed in claim 2, is characterized in that,
Described fat suppression pre-pulse be frequency selectivity make the longitudinal magnetization of fat to be greater than 90 degree and the flip angle the being less than 180 degree SPIR pulse carrying out toppling over,
The application time of described multiple ghost pulses is the time from the moment of the longitudinal flux cancellation of the fat of toppling over due to described SPIR pulse to the front end of described data collection train of pulse.
6. magnetic resonance imaging apparatus as claimed in claim 1, is characterized in that,
Described data collection train of pulse is the train of pulse collecting the echo data corresponding with phase code amount zero at first.
7. magnetic resonance imaging apparatus as claimed in claim 6, is characterized in that,
Described data collection train of pulse collects the train of pulse of echo data according to the order of following (a), (b) or (c), wherein,
A () is the order of the phase code amount based on center order;
B () increases from phase code amount zero to positive direction for phase code amount, change polarity and the order of phase code amount that direction from negative maximum towards zero is reduced after reaching positive maximum;
C () increases from phase code amount zero to negative direction for phase code amount, change polarity and the order of phase code amount that direction from positive maximum towards zero is reduced after reaching negative maximum.
8. magnetic resonance imaging apparatus as claimed in claim 2, is characterized in that,
Described data collection train of pulse is the train of pulse being dependent on FFE method and high speed field echo method.
9. magnetic resonance imaging apparatus as claimed in claim 8, is characterized in that,
The longitudinal magnetization of having got the fat of negative value in the applying by described fat suppression pre-pulse is restored between the moment of zero and the front end of train of pulse being dependent on described FFE method, multiple ghost pulses of the interval same intervals of multiple driving pulses and be dependent on described FFE method are set
Described ghost pulses flip angle separately sets be greater than described driving pulse flip angle separately.
10. magnetic resonance imaging apparatus as claimed in claim 9, is characterized in that,
Described ghost pulses flip angle is separately set to and gently increases.
11. 1 kinds of magnetic resonance imaging apparatus, is characterized in that possessing:
Configuration part, setting pulse train, this pulse train has fat suppression pre-pulse and the data collection train of pulse for collecting image reconstruction echo data, and, and then described data collection train of pulse is configured after described fat suppression pre-pulse, between the front end of the driving pulse corresponding with phase code amount zero in described data collection train of pulse and described data collection train of pulse, multiple driving pulses of the adjustable quantity corresponding with beyond phase code amount zero are set;
Data collection unit, applies based on the high-frequency impulse of the described pulse train set by described configuration part and gradient magnetic field pulses subject, and collects described echo data; And
Image production part, reconstructs the image of described subject according to collected described echo data.
12. magnetic resonance imaging apparatus as claimed in claim 11, is characterized in that,
Described data collection train of pulse is that its front end corresponds to negative phase code amount, phase code amount from described negative phase code to positive direction with the train of pulse that regulation amplitude increases, and the negative phase code amount of described front end can adjust.
13. magnetic resonance imaging apparatus as claimed in claim 11, is characterized in that,
Described data collection train of pulse is the train of pulse that its front end corresponds to positive phase code amount, phase code amount reduces with regulation amplitude from described positive phase code to negative direction, and the positive phase code amount of described front end can adjust.
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| KR20130049461A (en) * | 2011-11-04 | 2013-05-14 | 삼성전자주식회사 | Method for imaging magnetic resonance image and appratus using the same thereof |
| JP6045793B2 (en) * | 2012-01-13 | 2016-12-14 | 東芝メディカルシステムズ株式会社 | Magnetic resonance imaging device |
| JP6420583B2 (en) * | 2014-07-24 | 2018-11-07 | ジーイー・メディカル・システムズ・グローバル・テクノロジー・カンパニー・エルエルシー | Magnetic resonance apparatus and program |
| JP6956509B2 (en) * | 2017-04-21 | 2021-11-02 | キヤノンメディカルシステムズ株式会社 | Magnetic resonance imaging device |
| CN107369153B (en) * | 2017-07-18 | 2020-11-27 | 上海联影医疗科技股份有限公司 | Magnetic resonance fat inhibition image acquisition method, storage medium and scanning system |
| CN108363026A (en) * | 2018-03-05 | 2018-08-03 | 奥泰医疗系统有限责任公司 | A kind of black blood MR imaging method of fat compacting |
| CN109620228B (en) * | 2018-12-20 | 2023-01-03 | 上海联影医疗科技股份有限公司 | Fat zero offset correction method in magnetic resonance imaging and magnetic resonance imaging method |
| CN113805129B (en) * | 2020-06-11 | 2024-01-02 | 西门子(深圳)磁共振有限公司 | Data acquisition device and method and magnetic resonance imaging device |
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| US20180252787A1 (en) | 2018-09-06 |
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| CN103202693A (en) | 2013-07-17 |
| US9995811B2 (en) | 2018-06-12 |
| US20130193972A1 (en) | 2013-08-01 |
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